Annona Chalk
| Annona Chalk | |
|---|---|
| Stratigraphic range: Cretaceous | |
 Outcrop east of Clarksville, TX (c. 1910) | |
| Type | Sedimentary |
| Sub-units | Austin Group |
| Underlies | Marlbrook Marl |
| Overlies | Ozan Formation |
| Thickness | 30 Meters |
| Lithology | |
| Primary | Chalk |
| Location | |
| Region | Arkansas |
| Country | United States |
| Type section | |
| Named for | Annona, Red River County, Texas[1] |
| Named by | Robert Thomas Hill |
The Annona Chalk is a geologic formation in Arkansas, Texas, Louisiana, and Oklahoma.[2] It preserves fossils dating back to the Cretaceous period. The formation is a hard, thick-bedded to massive, slightly fossiliferous chalk. It weathers white, but is blue-gray when freshly exposed. The unit is commercially mined for cement. Fossils in the Annona Chalk include coelenterates, echinoderms, annelids, bivalves, gastropods, cephalopods, and some vertebrate traces.[3] The beds range in thickness, up to over 100 feet in depth in some areas (such as at White Cliffs).,[4] but thins to the east and is only a few feet thick north of Columbus, Arkansas and is completely missing to the east. The break between the Annona Formation and the Ozan Formation appears to be sharp with a few tubular borings up to a foot long extending down from the Annona in to the Ozan.[5]
Exposures
[edit | edit source]-
Annona Chalk overlying Ozan Formation at what is now called White Cliffs Natural Area, with the Little River in the foreground, Howard County, AR (c. 1910) -
Another view of the same location (c. 1902) -
Quarry at Whitecliffs Landing (c. 1902)
Paleofauna
[edit | edit source]- N. (Nostoceras) danei[6]
- N. (Nostoceras) monotuberculatum[6]
- N. (Nostoceras) plerucostatum[6]
- N. (Nostoceras) pulcher[6]
- O. crassum[6]
- A. ponderosana[7]
- B. rotunda[7]
- B. ovata[7]
- B. windhami[7]
- C. blakei[7]
- K. cushmani[7]
- L. fletcheri[7]
- O. hannai[7]
- P. texanus[7]
- V. ozanana[7]
See also
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References
[edit | edit source]- ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
- ^ USGS Geolex, Annona Chalk/Formation
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- ^ Dane, 1929, Upper Cretaceous Formations of Southwestern Arkansas, Arkansas Geological Survey Bulletin 1
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- Notes on the Annona Chalk, Norman L. Thomas and Elmer M. Rice, Journal of Paleontology, Vol. 6, No. 4 (Dec., 1932), pp. 319–329
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